Land ministry says climate change may be behind increase in landslide damage

Torrential rain possibly caused by climate change is the culprit for an increase in damages from landslides over the past 30 years, according to a recent survey.

Land ministry officials compiled statistics on landslide damage from 1984 that showed a 1.5-fold increase due to heavy rains.

With the frequency of torrential rains expected to increase in the future, there will be greater need for measures to deal with landslides.

A recent example of the destructive power of landslides occurred Oct. 16 on Izu-Oshima island south of Tokyo. Mudslides triggered by a typhoon were a major reason for 35 fatalities on the island. Four residents remain missing.

Ministry officials compared landslide statistics as of Nov. 5 with other years.

Between 1984 and 1993, an average 771 landslides took place over the course of a year. However, between 2004 and 2013, there were an average 1,178 landslides every year.

Limiting the damage just to mudslides like the ones that hit Izu-Oshima, there was a 1.5-fold increase between the yearly average of about 169 between 1984 and 1993, and the yearly average of about 249 between 2004 and 2013.

Japan Meteorological Agency statistics also show an increase in unprecedented heavy rains during the same time period.

Over the past decade, record amounts of rainfall have been set at over 600 of the 927 JMA observation points across Japan.

The rains that lashed Izu-Oshima last month were brought by Typhoon No. 26. A record rainfall of 824 millimeters was set over a 24-hour period, breaking the old record by more than 100 millimeters.

Land ministry officials have instructed prefectural governments to construct "sabo" (erosion and sediment control) facilities on the assumption of past record rainfall or rainfall amounts at an observation point that might occur once every 100 years.

However, an official with the Land Conservation Division of the Sabo (Erosion and Sediment Control) Department at the land ministry said, "There should have been a decrease in the number of destructive landslides with the building of such sabo facilities, but we believe there have been effects from global warming."

Izu-Oshima had such facilities, but they still did not prevent the deadly mudslides.

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